On 19/01/14 02:10, James Hogan wrote:
It appears that the following gcc patch adds support for #pragma pack: http://gcc.gnu.org/ml/gcc-patches/2006-10/msg01115.html
I gave it a quick spin on metag gcc (which is unfortunately stuck on an old version) and it seems to fix my simple test case so that #pragma pack(2) becomes equivalent to __packed __aligned(2) (for sizeof and __alignof__).
Then I personally think that it is better to fix metag gcc instead of changing the kernel.
Actually there are many different spots where "#pragma pack" is used. batman-adv is just the only one having compile time checks for structure sizes.
However, the __packed and __aligned are linux specific macros to abstract compiler details, whereas #pragma pack appears to be a compiler-specific WIN32 style equivalent to GCC's __attribute__((packed)) and __attribute__((aligned(2))) (these are what __packed and __aligned use in compiler-gcc.h).
Therefore I believe using the Linux abstractions is still more correct here.
If you really think so, I'd suggest to grep in the kernel and catch all the other occurrences of "#pragma pack" and change them all (assuming that using __attribute__((aligned(2))) is the way to go).
Cheers,